Ultrasonic diagnosis apparatuses have been frequently used when puncture using a puncture needle such as biopsy and radio frequency ablation (RFA) is performed, because they can display an ultrasonic image immediately below an ultrasound probe in real-time. If puncture is performed with a puncture guide attached to an ultrasound probe, the angle at which the puncture needle is inserted is limited. Puncture is therefore often performed freehand without using a puncture guide, based on the positional relationship between a lesion and a blood vessel. However, the puncture needle is sometimes obscured due to the effects of the position of a lesion or the introduction angle of the puncture needle. In such a case, puncture is performed by looking at the motion of tissues when the puncture needle is moved.
In recent years, a technique of generating an ultrasonic image (needle image) in which a puncture needle is imaged with high brightness has been known. In this technique, an oblique scan is performed by applying an ultrasonic beam perpendicular to a puncture needle in order to improve the visibility of the puncture needle during puncture. A technique of generating and displaying a composite image of a needle image and a living body image is also known, in which, in addition to generation of a needle image, an ultrasonic image (living body image) in which a living tissue is imaged is generated by performing a normal ultrasound scan without performing an oblique scan.
Objects whose brightness is increased by an oblique scan include not only a puncture needle but also a living tissue perpendicular to the transmission direction of ultrasound. When an oblique scan is performed, grating lobes are produced due to the beam shape and artifacts are produced in the image. Furthermore, the brightness of the puncture needle decreases as the puncture needle is displaced from immediately below the ultrasound probe. In particular when puncture is performed freehand, the angle of the puncture needle is not always constant.